Preparation of imides containing a fluorosulfonyl group

ABSTRACT

A process for preparing a fluoro compound of formula: R2—(SO2)—NX—(SO2)—F (III) including: (a) a first step for obtaining the chloro compound of formula: R1—(SO2)—NX—(SO2)—Cl; (II) this first step including the reaction of the sulfamide of formula: R0—(SO2)—NH2 (I) with a sulfurous acid and a chlorinating agent; and (b) a second step for obtaining the fluoro compound of formula (III), this second step including the reaction of the chloro compound of formula (II) with anhydrous hydrofluoric acid in at least one organic solvent; in which: X represents either a hydrogen atom or a monovalent cation M; R1 represents an electron-withdrawing group having a positive Hammett parameter σp; if R1 represents Cl, then R0 represents OH; otherwise, R0 is identical to R1; and if R1 represents Cl, then R2 represents F; otherwise, R2 is identical to R1.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.15/304,577, filed on Oct. 17, 2016, which is a U.S. national stage ofInternational Application No. PCT/FR2015/050845, filed on Apr. 1, 2015.The entire contents of each of U.S. application Ser. No. 15/304,577, andInternational Application No. PCT/FR2015/050845 are hereby incorporatedherein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to a process for preparing imidescontaining a fluorosulfonyl group.

TECHNICAL BACKGROUND

By virtue of their very low basicity, anions of sulfonylimide type areincreasingly used in the field of energy storage in the form ofinorganic salts in batteries, or of organic salts in supercapacitors orin the field of ionic liquids. Since the battery market is in fullexpansion and reduction of battery manufacturing costs has become amajor challenge, an inexpensive large-scale process for synthesizinganions of this type is necessary.

In the specific field of Li-ion batteries, the salt that is currentlythe most widely used is LiPF₆, but this salt has many drawbacks such aslimited thermal stability, sensitivity to hydrolysis and thus lowersafety of the battery. Recently, novel salts bearing the group FSO⁻²have been studied and have demonstrated many advantages such as betterion conductivity and resistance to hydrolysis. One of these salts, LiFSl(LiN(FSO₂)₂) has shown very advantageous properties which make it a goodcandidate for replacing LiPF₆.

Few processes for synthesizing LiFSl or the corresponding acid thereofhave been described, but it is clearly seen that, in all theseprocesses, the key step is the step of forming the S—F bond.

A first synthetic route described (Appel & Eisenbauer, Chem. Ber. 95,246-8, 1962) consists in reacting fluorosulfonic acid (FSO₃H) with urea.However, the corrosive and toxic nature of this compound does not allowindustrialization of the process.

EP 2 415 709 describes a process based on this route, in which theproducts of reaction of fluorosulfonic acid with urea are dissolved inwater and bis(fluorosulfonyl)imide is precipitated in the form of thesalt with tetrabutylammonium. This synthetic route is not viable on alarge scale since the overall yield is very low.

Another route consists in reacting difluorosulfoxide with ammonia: seeWO 2010/113 835 in this regard. However, this method also forms numerousside products, which necessitates expensive purification steps.

Another route (Ruff & Lustig, Inorg. Synth. 1968, 11, 138-43) consistsin synthesizing in a first stage a dichloro compound of formula(ClSO₂)₂NH and then in performing a chlorine/fluorine exchange withAsF₃. However, this process is not industrializable due to the highprice and the toxicity of AsF₃.

WO 02/053 494 describes another route which consists of a Cl/F exchangeon (ClSO₂)₂NH using a fluoride of a monovalent cation which may bealkaline or of onium type (NR₄ ⁺), in an aprotic solvent. However,according to said document, the reaction is very slow.

Example 10 of WO 2007/068 822 describes the synthesis ofbis(fluorosulfonyl)imide in anhydrous hydrofluoric acid (HF). Thus, thereaction is performed in an autoclave with 1 g ofbis(chlorosulfonyl)imide and 4 g of anhydrous HF at various reactiontemperatures and times. The document teaches that even at temperaturesof 130° C., the reaction yield does not exceed 55%. In addition, itteaches that the presence of impurities makes separation difficult atthe industrial scale. It concluded that the synthesis ofbis(fluorosulfonyl)imide with HF is unsatisfactory, and thus that theuse of a lithium fluoride is preferred during the chlorine/fluorineexchange step.

WO 2009/123 328 describes the manufacture of sulfonylimide compounds,via a reaction between amidosulfuric acid and thionyl chloride and thenwith chlorosulfonic acid, to form bis(chlorosulfonyl)imide, which isthen subjected to a fluorination step. The fluorination is performedwith a fluoro compound such as CuF₂, ZnF₂, SnF₂, PbF₂ or BiF₃. However,these fluoro compounds are expensive, making the exploitation of theprocess at the industrial scale difficult.

There is thus still a need to produce imides containing a sulfonyl group(such as LiFSI), especially via a process that can be performed at theindustrial scale.

SUMMARY OF THE INVENTION

The invention relates firstly to a process for preparing a fluorocompound of formula:

R₂—(SO₂)—NX—(SO₂)—F  (III)

comprising:

(a) a first step for obtaining the chloro compound of formula:

R₁—(SO₂)—NX—(SO₂)—Cl;  (II)

-   -   this first step comprising the reaction of the sulfamide of        formula:

R₀—(SO₂)—NH₂  (I)

-   -   with a sulfurous acid and a chlorinating agent; and

(b) a second step for obtaining the fluoro compound of formula (III),this second step comprising the reaction of the chloro compound offormula (II) with anhydrous hydrofluoric acid in at least one organicsolvent;

in which:

-   -   X represents either a hydrogen atom or a monovalent cation M;    -   R₁ represents an electron-withdrawing group having a positive        Hammett parameter σ_(p);    -   if R₁ represents Cl, then R₀ represents OH; otherwise, R₀ is        identical to R₁; and    -   if R₁ represents Cl, then R₂ represents F; otherwise, R₂ is        identical to R₁.

According to one embodiment, R₁ is chosen from Cl, F, CF₃, CHF₂, CH₂F,C₂HF₄, C₂H₂F₃, C₂H₃F₂, C₂F₅, C₃F₇, C₃H₂F₅, C₃H₄F₃, C₃HF₆, C₄F₉, C₄H₂F₇,C₄H₄F₅, C₅F₁₁, C₃F₆OCF₃, C₂F₄OCF₃, C₂H₂F₂OCF₃, CF₂OCF₃, C₆F₁₃, C₇F₁₅,C₈F₁₇ and C₉F₁₉.

According to one embodiment, M represents an alkali metal oralkaline-earth metal cation or a quaternary ammonium cation, andpreferably M represents a lithium or sodium cation and more particularlypreferably a lithium cation.

According to one embodiment, the sulfurous acid used in the first stepis chosen from chlorosulfonic acid, sulfuric acid, oleum and mixturesthereof.

According to one embodiment, the chlorinating agent used in the firststep is chosen from thionyl chloride, oxalyl chloride, phosphoruspentachloride, phosphonyl trichloride, phosphoryl trichloride andmixtures thereof.

According to one embodiment:

-   -   a catalyst is used for the reaction of the sulfamide with the        sulfurous acid and the chlorinating agent in the first step,        which is preferably chosen from a tertiary amine such as        methylamine, triethylamine or diethylmethylamine, or pyridine        and derivatives thereof such as 2,6-lutidine; and/or    -   the reaction of the sulfamide with the sulfurous acid and the        chlorinating agent in the first step is performed at a        temperature of between 30 and 150° C.; and/or    -   the reaction of the sulfamide with the sulfurous acid and the        chlorinating agent in the first step is performed at a pressure        of between 1 and 7 bar absolute.

According to one embodiment:

-   -   the mole ratio between the sulfurous acid and the sulfamide used        in the first step is between 1 and 5; and/or    -   the mole ratio between the chlorinating agent and the sulfamide        used in the first step is between 1 and 10.

According to one embodiment, the organic solvent in the second step hasa donor number of between 1 and 70 and advantageously between 5 and 65.

According to one embodiment, the organic solvent in the second step ischosen from esters, nitriles, dinitriles, ethers, diethers, amines andphosphines, and mixtures thereof.

According to one embodiment:

-   -   the reaction of the chloro compound of formula (II) with        anhydrous hydrofluoric acid of the second step is performed at a        temperature of between 0° C. and the boiling point of the        organic solvent, preferably between 5° C. and the boiling point        of the organic solvent; and/or    -   the reaction of the chloro compound of formula (II) with        anhydrous hydrofluoric acid of the second step is performed at a        pressure of between 0 and 16 bar absolute.

According to one embodiment, the chloro compound of formula (II) isdissolved in the organic solvent prior to the second reaction step.

According to one embodiment:

-   -   the mass ratio between the chloro compound of formula (II) and        the organic solvent used in the reaction of the chloro compound        of formula (II) with anhydrous hydrofluoric acid of the second        step is between 0.001 and 10 and preferably between 0.005 and 5;        and/or    -   the mole ratio between the chloro compound of formula (II) and        hydrofluoric acid used in the reaction of the chloro compound of        formula (II) with anhydrous hydrofluoric acid of the second step        is between 0.01 and 0.5 and preferably between 0.05 and 0.5.

According to one embodiment, the reaction of the sulfamide with thesulfurous acid and the chlorinating agent of the first step provides thechloro compound of formula:

R₁—(SO₂)—NH—(SO₂)—Cl;  (IIa)

the first step also comprising the reaction of the chloro compound offormula (IIa) with a base, for obtaining the chloro compound of formula:

R₁—(SO₂)—NM—(SO₂)—Cl;  (IIb)

in which M represents a monovalent cation.

According to one embodiment, said base is chosen from alkali metalcarbonates, alkaline-earth metal carbonates, alkali metal hydroxides,alkaline-earth metal hydroxides, tertiary amines in a polar organicsolvent, and mixtures thereof.

According to one embodiment, the process comprises, after the secondstep:

(c) a third step of neutralization of the compound of formula (III),preferably by adding a base chosen from alkali metal carbonates,alkaline-earth metal carbonates, alkali metal hydroxides, alkaline-earthmetal hydroxides and mixtures thereof.

According to one embodiment, the fluoro compound of formula (III)obtained in the second step is a compound of formula:

R₂—(SO₂)—NH—(SO₂)—F  (IIIa)

and the third step of neutralization allows the compound of formula(IIIa) to be converted into a compound of formula:

R₂—(SO₂)—NM—(SO₂)—F  (IIIb)

in which M represents a monovalent cation.

According to one embodiment, the process comprises, after the secondstep or, where appropriate, the third step, a final step of cationexchange, preferably by placing in contact with an alkali metal oralkaline-earth metal or quaternary ammonium fluoride, chloride,carbonate, hydroxide, sulfate, chlorate, perchlorate, nitrite ornitrate.

According to one embodiment, the process makes it possible to obtainLiN(FSO₂)₂, LiN(SO₂CF₃)(SO₂F), LiN(SO₂C₂F₅)(SO₂F),LiN(SO₂CF₂OCF₃)(SO₂F), LiN(SO₂C₃HF₆)(SO₂F), LiN(SO₂C₄F₉)(SO₂F),LiN(SO₂C₅F₁₁)(SO₂F), LiN(SO₂C₆F₁₃)(SO₂F), LiN(SO₂C₇F₁₅)(SO₂F),LiN(SO₂C₈F₁₇)(SO₂F) or LiN(SO₂C₉F₁₉)(SO₂F), and preferably LiN(FSO₂)₂.

The invention also relates to a process for manufacturing anelectrolyte, comprising the preparation of an imide salt of formula(IIIb) R₂—(SO₂)—NM—(SO₂)—F, in which M represents a monovalent cationand R₂ represents an electron-withdrawing group having a positiveHammett parameter σ_(p), via the process described above, anddissolution thereof in a solvent, said imide salt preferably being alithium or sodium salt.

The invention also relates to a process for manufacturing a battery or abattery cell, comprising the manufacture of an electrolyte according tothe above process and the insertion of this electrolyte between an anodeand a cathode.

The invention also relates to a composition comprising at least 99.9% bymass of an imide salt of formula:

R₂—(SO₂)—NM—(SO₂)—F  (IIIb)

in which M represents a monovalent cation and R₂ represents anelectron-withdrawing group having a positive Hammett parameter σ_(p),the composition comprising a mass content of total fluorides of from 1to 500 ppm, and/or a mass content of total chlorides of from 1 to 200ppm.

According to one embodiment, the mass content of total fluorides is from1 to 250 ppm and/or the mass content of total chlorides is from 1 to 100ppm.

According to one embodiment, the composition comprises a mass content ofnitrates of less than or equal to 250 ppm, preferably less than or equalto 150 ppm; and/or a mass content of sulfates of less than or equal to250 ppm, preferably less than or equal to 150 ppm.

According to one embodiment:

-   -   M represents Li or Na; and/or    -   R₂ represents F, CF₃, CHF₂, CH₂F, C₂HF₄, C₂H₂F₃, C₂H₃F₂, C₂F₅,        C₃F₇, C₃H₂F₅, C₃H₄F₃, C₃HF₆, C₄F₉, C₄H₂F₇, C₄H₄F₅, C₅F₁₁,        C₃F₆OCF₃, C₂F₄OCF₃, C₂H₂F₂OCF₃, CF₂OCF₃, C₆F₁₃, C₇F₁₅, C₈F₁₇ or        C₉F₁₉, F being preferred.

According to one embodiment, the imide salt is LiN(FSO₂)₂,LiN(SO₂CF₃)(SO₂F), LiN(SO₂C₂F₅)(SO₂F), LiN(SO₂CF₂OCF₃)(SO₂F),LiN(SO₂C₃HF₆)(SO₂F), LiN(SO₂C₄F₉)(SO₂F), LiN(SO₂C₅F₁₁)(SO₂F),LiN(SO₂C₆F₁₃)(SO₂F), LiN(SO₂C₇F₁₅)(SO₂F), LiN(SO₂C₈F₁₇)(SO₂F) orLiN(SO₂C₉F₁₉)(SO₂F), and preferably LiN(FSO₂)₂.

The present invention makes it possible to overcome the drawbacks of theprior art. The invention more particularly provides a process forproducing imides containing a sulfonyl group (such as LiFSI) which maybe performed at the industrial scale, and without entailing excessivecost.

This is mainly accomplished by means of the fluorination reaction of abis(sulfonyl)imide chloro compound with anhydrous hydrofluoric acid inan organic solvent. It has been observed, surprisingly, that thisfluorination reaction gives a yield of greater than 70%.

Thus, the Applicant has overturned the preconception illustrated in WO2007/068 822.

DETAILED DESCRIPTION

The invention is now described in greater detail and in a nonlimitingmanner in the description that follows.

The invention involves preparing a compound comprising at least onefluorosulfonyl group according to a general scheme in at least twosteps:

(a) Preparation of a compound comprising at least one chlorosulfonylgroup.

(b) Fluorination of the compound from step (a).

In addition, a third step may optionally be envisaged:

(c) Neutralization of the compound from step (b).

In addition, a fourth step may optionally be envisaged, either after thethird step or directly after the second step:

(d) Cation exchange.

Step (a)

In step (a), the sulfamide of formula (I) R₀—(SO₂)—NH₂ is reacted with asulfurous acid and a chlorinating agent, so as to obtain a chlorocompound of formula (II) R₁—(SO₂)—NX—(SO₂)—Cl.

X represents either a hydrogen atom or a monovalent cation denoted M.

When X represents a hydrogen atom, the above chloro compound is thecompound of formula (IIa) R₁—(SO₂)—NH—(SO₂)—Cl.

When X represents a monovalent cation, the chloro compound is the saltof formula (IIb) R₁—(SO₂)—NM—(SO₂)—Cl, which may also be written asR₁—(SO₂)—N⁻¹—(SO₂)—Cl, M⁺.

As monovalent cation, use may be made of an alkali metal oralkaline-earth metal cation or a quaternary ammonium cation. Sodium and,especially, lithium are preferred.

When the chloro compound (II) obtained on conclusion of the first stepis the compound of formula (IIa), the reaction of the sulfamide with thesulfurous acid and the chlorinating agent makes it possible to obtainthe chloro compound directly.

When the chloro compound (II) obtained on conclusion of the first stepis the compound of formula (IIb), the process is performed in twostages:

-   -   in a first stage, reaction of the sulfamide with the sulfurous        acid and the chlorinating agent, which makes it possible to        obtain the chloro compound of formula (IIa):    -   in a second stage, conversion of the chloro compound of formula        (IIa) into the chloro compound of formula (IIb) by reaction with        a base.

In all cases, R₁ represents an electron-withdrawing group having apositive Hammett parameter σ_(p).

R₁ may especially represent Cl, F or an alkyl or alkoxyalkyl groupcomprising from 1 to 9 carbon atoms, and totally or partiallysubstituted with fluorine. Examples of such groups are the groups: CF₃,CHF₂, CH₂F, C₂HF₄, C₂H₂F₃, C₂H₃F₂, C₂F₅, C₃F₇, C₃H₂F₅, C₃H₄F₃, C₃HF₆,C₄F₉, C₄H₂F₇, C₄H₄F₅, C₅F₁₁, C₃F₆OCF₃, C₂F₄OCF₃, C₂H₂F₂OCF₃, CF₂OCF₃,C₆F₁₃, C₇F₁₅, C₈F₁₇ and C₉F₁₉.

When R₁ represents Cl, then the starting sulfamide is the amidosulfonicacid of formula (I′) OH—(SO₂)—NH₂ (R₀ represents OH).

When R₁ represents another group, then the starting sulfamide has theformula (I″) R₁—(SO₂)—NH₂ (R₀ is identical to R₁).

The sulfurous acid used for the reaction may be chlorosulfonic acidClSO₃H, or alternatively sulfuric acid or oleum. Combinations of thesereagents may also be used.

The chlorinating agent used for the reaction may be chosen from thionylchloride SOCl₂, oxalyl chloride (COCl)₂, phosphorus pentachloride PCl₅,phosphonyl trichloride PCl₃ and phosphoryl trichloride POCl₃.Combinations of these reagents may also be used.

A catalyst may also be used to accelerate the reaction, chosen, forexample, from a tertiary amine such as methylamine, triethylamine ordiethylmethylamine. Use may also be made of pyridine or a derivativethereof such as 2,6-lutidine. The mole ratio between the sulfurous acidand the sulfamide is advantageously between 1 and 5. The mole ratiobetween the chlorinating agent and the sulfamide is advantageouslybetween 1 and 10, and more particularly: between 1 and 5 when thesulfurous acid is chlorosulfonic acid; and between 2 and 10 when thesulfurous acid is sulfuric acid or oleum.

The reaction temperature is advantageously between 30 and 150° C. Thereaction time is advantageously between 1 hour and 7 days. The reactionmay advantageously be performed at a pressure of between 1 bar absoluteand 7 bar absolute.

The reaction leads to an evolution of HCl gas and also other gases whichmay be, for example, depending on the chlorinating agent used, CO, CO₂or SO₂.

The possible unreacted reagents or degraded products in solution may beremoved via a step of purification by filtration or by recrystallizationfrom an apolar solvent such as pentane, toluene or cyclohexane.

As regards the optional reaction for conversion of the chloro compoundof formula (IIa) into the chloro compound (salt) of formula (IIb), theprocess is performed by reacting the chloro compound of formula (IIa)with a base which may be, for example, an alkali metal or alkaline-earthmetal carbonate, an alkali metal or alkaline-earth metal hydroxide or amixture thereof, or alternatively at least one tertiary amine in anorganic solvent of polar type.

As organic solvent of polar type, use may be made especially ofacetonitrile, dioxane, tetrahydrofuran, ethyl acetate, butyl acetate andcombinations thereof.

This reaction may be performed by dissolving the chloro compound offormula (IIa) in the organic solvent, for example at a concentration of10⁻³ to 10 mol/L. The base may be added in liquid or solid form. Thebase/chloro compound of formula (IIa) mole ratio may be, for example, 1when the base is a hydroxide or an amine, or 2 when the base is acarbonate. The reaction temperature may be, for example, between −10° C.and 40° C.

At the end of the reaction, the excess base may be filtered off, and thesolution may be evaporated.

Step (b)

In step (b), the chloro compound of formula (IIa) or of formula (IIb)obtained on conclusion of step (a) is fluorinated, so as to obtain thefluoro compound of formula (III) R₁—(SO₂)—NX—(SO₂)—F.

When the fluorination involves a chloro compound of formula (IIa), thefluoro compound obtained is the compound of formula (IIIa)R₂—(SO₂)—NH—(SO₂)—F.

When the fluorination involves a chloro compound of formula (IIb), thefluoro compound obtained is the salt of formula (IIIb)R₂—(SO₂)—NM—(SO₂)—F, which may also be written as R₂—(SO₂)—N—(SO₂)—F,M³⁰ .

When R₁ represents Cl, R₂ represents F.

In all the other cases, R₂ is identical to R₁ as defined above.

Preferably, R₂ represents F, CF₃, CHF₂, CH₂F or CF₂OCF₃. It isparticularly preferred for R₂ to represent F.

The fluorination reaction uses anhydrous hydrofluoric acid (HF) in anorganic solvent.

The organic solvent preferably has a donor number of between 1 and 70and advantageously between 5 and 65. The donor number of a solventrepresents the value −ΔH, ΔH being the enthalpy of the interactionbetween the solvent and antimony pentachloride (according to the methoddescribed in Journal of Solution Chemistry, vol. 13, No. 9, 1984).Organic solvents that may especially be mentioned include esters,nitriles or dinitriles, ethers or diethers, amines and phosphines.Combinations thereof may also be used as organic solvent.

Methyl acetate, ethyl acetate, butyl acetate, acetonitrile,propionitrile, isobutyronitrile, glutaronitrile, dioxane,tetrahydrofuran, triethylamine, tripropylamine, diethylisopropylamine,pyridine, trimethylphosphine, triethylphosphine,diethylisopropylphosphine and mixtures thereof may especially besuitable for use as organic solvents.

The reaction with anhydrous HF may be performed at a temperaturepreferably between 0° C., preferably 20° C., and the boiling point ofthe organic solvent used. Advantageously, this temperature is between 5°C., preferably 25° C., and the boiling point of the organic solvent.

According to the present invention, the step of reaction with anhydrousHF is performed at a pressure that is preferably between 0 and 16 barabsolute.

The chloro compound of formula (II) is preferably dissolved in theorganic solvent before the step of reaction with anhydrous HF.

The mass ratio between the chloro compound of formula (II) and theorganic solvent is preferably between 0.001 and 10, and advantageouslybetween 0.005 and 5.

HF is introduced into the reaction medium preferably in gaseous form.

The mole ratio between the chloro compound of formula (II) and the HFused is preferably between 0.01 and 0.5, and advantageously between 0.05and 0.5.

The step of reaction with HF may be performed in a closed medium or inan open medium.

Without wishing to be bound by a theory, the Applicant considers thatthe use of a donor organic solvent makes it possible to form asolvent-HF complex and thus to enhance the nucleophilicity of thefluorine atom. The use of such a complex allows mild fluorination of thechloro compound of formula (II), thus avoiding spurious cleavagereactions.

The process according to the present invention makes it possible toobtain fluorination yields of between 85% and 100%, which represents amarked increase in comparison with the prior art processes.

The fluorination reaction leads to the formation of HCl, the majority ofwhich may be degassed from the reaction medium (just like the excessHF), for example by sparging with a neutral gas (such as nitrogen,helium or argon).

However, the residual HF and/or HCl may be dissolved in the reactionmedium. In the case of HCl, the amounts are very low since, at theworking pressure and temperature, HCl is mainly in gas form.

Step (c)

After step (b), the reaction medium is thus preferably neutralized, forexample using an aqueous solution of an alkali metal or alkaline-earthmetal carbonate M′CO₃·nH₂O or of an alkali metal or alkaline-earth metalhydroxide M′OH·nH_(Z)O preferably to obtain a pH of greater than 4. Usemay also be made of mixtures of the above carbonates and/or hydroxides.

In the foregoing, M′ denotes a monovalent alkali metal or alkaline-earthmetal cation.

The residual HF and/or the residual HCl dissolved in the solvent reactswith the above carbonate or hydroxide, so as to form an alkali metal oralkaline-earth metal fluoride M′F (or a mixture of fluorides M′F), or,respectively, an alkali metal or alkaline-earth metal chloride M′Cl (ora mixture of chlorides M′Cl).

The neutralization reaction may be performed, for example, by adding anaqueous solution of the chosen base. The base/fluoro compound of formula(III) mole ratio may be, for example, from 1 to 5 when the base is ahydroxide, or from 0.5 to 5 or from 2 to 10 when the base is acarbonate. The reaction temperature may be, for example, between −10° C.and 40° C.

At the end of the reaction, the excess base may be filtered off, and thesolution may be evaporated. This also allows removal of the majority ofthe fluorides and chlorides formed.

The solution may then be extracted with an organic solvent, which maybe, for example, dichloromethane, acetonitrile, ethyl acetate, butylacetate, diethyl ether, tetrahydrofuran, toluene or a mixture thereof.This extraction may be performed several times to maximize the recoveryyield.

The organic phase obtained may then be extracted several times withwater to purify the product. The organic solution may then be evaporatedto give the desired imide salt containing a fluorosulfonyl group.

The imide salt thus obtained preferably has a mass content of fluoridesof less than 500 ppm and more particularly preferably less than 250 ppm.

The imide salt thus obtained also preferably has a mass content ofchlorides of less than 200 ppm and more particularly preferably lessthan 100 ppm.

It should be noted that, in the particular case in which the fluorocompound of formula (IIIa) R₂—(SO₂)—NH—(SO₂)—F is obtained on conclusionof the second step, the third step of neutralization as described abovealso leads toward converting this compound into the fluoro compound(salt) of formula (IIIb) R₂—(SO₂)—NM—(SO₂)—F, M being equal to M′.

Step (d)

Optionally, a step of cation exchange may be envisaged at the end of theprocess. This step makes it possible to convert a fluoro compound offormula (IIIb) R₂—(SO₂)—NM—(SO₂)—F into a fluoro compound of formula(IIIc) R₂—(SO₂)—NM″—(SO₂)—F, in which M″ represents a cation.

M″ may especially represent an alkali metal or alkaline-earth metalcation or a quaternary ammonium cation. It may be, for example, thelithium or sodium cation, more particularly the lithium cation.

This step of cation exchange is performed by placing the fluoro compoundof formula (IIIb) in contact with a salt of the cation M″, which may bea fluoride, chloride, carbonate, hydroxide, sulfate, chlorate,perchlorate, nitrite or nitrate salt. A combination of these compoundsmay also be used.

The reaction may be performed, for example, in water or in a polarorganic solvent especially such as acetonitrile, N-methylpyrrolidone,dimethylformamide, dimethyl sulfoxide, nitromethane, dioxane,tetrahydrofuran, ethyl acetate, butyl acetate and mixtures thereof.

The reaction may be performed, for example, at a temperature of between0° and the boiling point of the solvent used.

The reaction time may be, for example, between 1 hour and 5 days.

The mole ratio between the salt of the cation M″ and the imide salt maybe, for example, between 0.9 and 5. The concentration of imide salt inwater or the organic solvent may be, for example, between 0.001 and 5mol/L.

In the particular case in which the solvent used is water, the reactionmedium may then be extracted with an organic solvent which mayespecially be dichloromethane, acetonitrile, ethyl acetate, butylacetate, diethyl ether, tetrahydrofuran, toluene or mixtures thereof.This extraction may be performed several times to maximize the recoveryyield. The organic phase is then evaporated to obtain the imide salt offormula (IIIc).

The process according to the present invention is particularlyadvantageous for manufacturing the following imide salts: LiN(SO₂F)₂,LiNSO₂CF₃SO₂F, LiNSO₂C₂F₅SO₂F, LiNSO₂CF₂OCF₃SO₂F, LiNSO₂C₃HF₆SO₂F,LiNSO₂C₄F₉SO₂F, LiNSO₂C₅F₁₁SO₂F, LiNSO₂C₆F₁₃SO₂F, LiNSO₂C₇F₁₅SO₂F,LiNSO₂C₈F₁₇SO₂F and LiNSO₂C₉F₁₉SO₂F.

Preferably, these salts are obtained in a purity at least equal to 99.5%by weight, advantageously at least equal to 99.9% by weight.

The impurities such as LiCl, LiF or NaCl, NaF and FSO₃Na that may bepresent in the imide salt each preferably represent less than 1000 ppm,advantageously less than 500 ppm.

The impurity FSO₃Li may be present in a concentration of less than 50ppm, preferably less than 5 ppm.

The nitrates and sulfates that may be present in the imide salt areadvantageously, respectively, present in a mass concentration of lessthan 250 ppm and preferably less than 150 ppm.

As indicated previously, the content of fluorides that may be present ispreferably less than 500 ppm, and more particularly preferably less than250 ppm.

As indicated previously, the content of chlorides that may be present ispreferably less than 200 ppm, and more particularly preferably less than100 ppm.

These concentrations of impurities are mass concentrations relative tothe mass of the desired imide salt.

The imide salt obtained is preferably essentially free of water and ofimpurities constituted by salts formed from a cation derived from groups11 to 15 and periods 4 to 6 of the Periodic Table (for example Zn, Cu,Sn, Pb, Bi).

These impurities are harmful to the performance of Li-ion or Na-ionbatteries on account of their electrochemical activity.

Preparation of an Electrolyte

The imide salt prepared as described above may be used for thepreparation of an electrolyte, by dissolving it in a suitable solvent.

For example, as described in the document J. Electrochemical Society,2011, 158, A74-82, LiFSI may be dissolved to a concentration of 1 mol/Lin a mixture of ethylene carbonate (EC), dimethyl carbonate (DMC) andethyl methyl carbonate (EMC) at 5 to 2 to 3 by volume; such anelectrolyte shows very good conductivity, good cycling stability andcorrosion of aluminum above 4.2 V.

This electrolyte may then be used for the manufacture of batteries orbattery cells, by placing it between a cathode and an anode, in a mannerknown per se.

EXAMPLES

The examples that follow illustrate the invention without limiting it.

Example 1

Sulfamic acid (1 eq., 0.515 mol, 50 g) is placed in a round-bottomedflask with thionyl chloride (3.75 eq., 1.93 mol, 229.8 g) and 95%sulfuric acid (1 eq., 0.515 mol, 53.1 g) is added at room temperature.The mixture is maintained at the reflux point of the thionyl chloridefor 24 hours with stirring. The dichloro compound finally obtained ispale yellow in appearance, with residual undissolved sulfamic acid. Themixture is filtered to remove the sulfamic acid (23.6 g) and the thionylchloride is then evaporated off under vacuum.

Example 2

1 eq. of sulfamic acid (0.25 mol, 24.25 g) is placed in a glassround-bottomed flask or reactor, followed by thionyl chloride (2.75 eq.,0.69 mol, 81.9 g). Next, chlorosulfonic acid (2 eq., 0.5 mol, 58.25 g)is added very slowly with stirring at room temperature. The mixture isbrought gradually to the reflux point of the thionyl chloride (oil bathat 90° C.) and is left at reflux for 24 hours, with continued stirring.Evolution of gas is observed, this gas being trapped in water at thereactor outlet. The product finally recovered in the round-bottomedflask is liquid, slightly orange and highly fuming.

Example 3

28 g of (ClSO₂)₂NH are dissolved in 50 mL of acetonitrile in an 800 mLautoclave. 10 g of HF are then added. The pressure is then 0.34 barabsolute and the temperature is maintained at 10° C. The reaction isleft stirring in a closed medium for 18 hours. The excess HF is removedby flushing with an inert gas. The reaction medium is then treated withlithium carbonate. The solution is filtered and then evaporated and theresidue is analyzed by ¹⁹F NMR. The analysis shows the presence of 85%of totally fluorinated product (FSO₂)₂NLi, 7.5% of FSO₃Li and 7.5% ofFSO₂NH₂. These last two products are the compounds formed during thedegradation of the starting material.

Example 4

31.7 g of (ClSO₂)₂NH are dissolved in 50 mL of acetonitrile in an 800 mLautoclave. 10 g of HF are then added. The pressure is then 0.75 barabsolute and the temperature is maintained at 20° C. The reaction isleft stirring in a closed medium for 18 hours. The excess HF is removedby pumping. The reaction medium is then treated with lithium carbonate.

The solution is filtered and then evaporated and the residue is analyzedby ¹⁹F NMR. The analysis shows the presence of 100% of totallyfluorinated product (FSO₂)₂NLi and the absence of the degradationproducts FSO₃Li and FSO₂NH₂.

Example 5

61 g of (ClSO₂)₂NH are dissolved in 50 mL of 1,4-dioxane in an 800 mLautoclave. 20 g of HF are then added. The pressure is then 2.3 barabsolute and the temperature is maintained at 25° C. The reaction isleft stirring in a closed medium for 18 hours. The excess HF is removedby pumping. The reaction medium is then treated with lithium carbonate.The solution is filtered and then evaporated and the residue is analyzedby ¹⁹F NMR. The analysis shows the presence of 100% of totallyfluorinated product (FSO₂)₂NLi and the absence of the degradationproducts FSO₃Li and FSO₂NH₂.

Example 6

65 g of (ClSO₂)₂NH are dissolved in 50 mL of 1,4-dioxane in an 800 mLautoclave. 20 g of HF are then added. The pressure is then 0 barabsolute and the temperature is maintained at 25° C. The reaction isleft stirring in an open medium for 3 hours. The excess HF is removed byflushing with an inert gas. The reaction medium is then treated withlithium carbonate. The solution is filtered and then evaporated and theresidue is analyzed by ¹⁹F NMR. The analysis shows the presence of 100%of totally fluorinated product (FSO₂)₂NLi and the absence of thedegradation products FSO₃Li and FSO₂NH₂.

EMBODIMENTS

1. A process for preparing a fluoro compound of formula:

R₂—(SO₂)—NX—(SO₂)—F  (III)

comprising:

(a) a first step for obtaining the chloro compound of formula:

R₁—(SO₂)—NX—(SO₂)—Cl;  (II)

-   -   this first step comprising the reaction of the sulfamide of        formula:

R₀—(SO₂)—NH₂  (I)

-   -   with a sulfurous acid and a chlorinating agent; and

(b) a second step for obtaining the fluoro compound of formula (Ill),this second step comprising the reaction of the chloro compound offormula (II) with anhydrous hydrofluoric acid in at least one organicsolvent; in which:

-   -   X represents either a hydrogen atom or a monovalent cation M;    -   R₁ represents an electron-withdrawing group having a positive        Hammett parameter σ_(p);    -   if R₁ represents Cl, then R₀ represents OH; otherwise, R₀ is        identical to R₁; and    -   if R₁ represents Cl, then R₂ represents F; otherwise, R₂ is        identical to R₁.        2. The process as in embodiment 1, in which R₁ is chosen from        Cl, F, CF₃, CHF₂, CH₂F, C₂HF₄, C₂H₂F₃, C₂H₃F₂, C₂F₅, C₃F₇,        C₃H₂F₅, C₃H₄F₃, C₃HF₆, C₄F₉, C₄H₂F₇, C₄H₄F₅, C₅F₁₁, C₃F₆OCF₃,        C₂F₄OCF₃, C₂H₂F₂OCF₃, CF₂OCF₃, C₆F₁₃, C₇F₁₅, C₈F₁₇ and C₉F₁₉.        3. The process as in embodiment 1 or 2, in which M represents an        alkali metal or alkaline-earth metal cation or a quaternary        ammonium cation, and in which, preferably, M represents a        lithium or sodium cation and more particularly preferably a        lithium cation.        4. The process as in one of embodiments 1 to 3, in which the        sulfurous acid used in the first step is chosen from        chlorosulfonic acid, sulfuric acid, oleum and mixtures thereof.        5. The process as in one of embodiments 1 to 4, in which the        chlorinating agent used in the first step is chosen from thionyl        chloride, oxalyl chloride, phosphorus pentachloride, phosphonyl        trichloride, phosphoryl trichloride and mixtures thereof.        6. The process as in one of embodiments 1 to 5, in which:    -   a catalyst is used for the reaction of the sulfamide with the        sulfurous acid and the chlorinating agent in the first step,        which is preferably chosen from a tertiary amine such as        methylamine, triethylamine or diethylmethylamine, or pyridine        and derivatives thereof such as 2,6-lutidine; and/or    -   the reaction of the sulfamide with the sulfurous acid and the        chlorinating agent in the first step is performed at a        temperature of between 30 and 150° C.; and/or    -   the reaction of the sulfamide with the sulfurous acid and the        chlorinating agent in the first step is performed at a pressure        of between 1 and 7 bar absolute.        7. The process as in one of embodiments 1 to 6, in which:    -   the mole ratio between the sulfurous acid and the sulfamide used        in the first step is between 1 and 5; and/or    -   the mole ratio between the chlorinating agent and the sulfamide        used in the first step is between 1 and 10.        8. The process as in one of embodiments 1 to 7, in which the        organic solvent in the second step has a donor number of between        1 and 70, and advantageously between 5 and 65.        9. The process as in one of embodiments 1 to 8, in which the        organic solvent in the second step is chosen from esters,        nitriles, dinitriles, ethers, diethers, amines and phosphines,        and mixtures thereof.        10. The process as in one of embodiments 1 to 9, in which:    -   the reaction of the chloro compound of formula (II) with        anhydrous hydrofluoric acid of the second step is performed at a        temperature of between 0° C. and the boiling point of the        organic solvent, preferably between 5° C. and the boiling point        of the organic solvent; and/or    -   the reaction of the chloro compound of formula (II) with        anhydrous hydrofluoric acid of the second step is performed at a        pressure of between 0 and 16 bar absolute.        11. The process as in one of embodiments 1 to 10, in which the        chloro compound of formula (II) is dissolved in the organic        solvent prior to the second reaction step.        12. The process as in one of embodiments 1 to 11, in which:    -   the mass ratio between the chloro compound of formula (II) and        the organic solvent used in the reaction of the chloro compound        of formula (II) with anhydrous hydrofluoric acid of the second        step is between 0.001 and 10 and preferably between 0.005 and 5;        and/or    -   the mole ratio between the chloro compound of formula (II) and        hydrofluoric acid used in the reaction of the chloro compound of        formula (II) with anhydrous hydrofluoric acid of the second step        is between 0.01 and 0.5 and preferably between 0.05 and 0.5.        13. The process as in one of embodiments 1 to 12, in which the        reaction of the sulfamide with the sulfurous acid and the        chlorinating agent of the first step provides the chloro        compound of formula:

R₁—(SO₂)—NH—(SO₂)—Cl;  (IIa)

the first step also comprising the reaction of the chloro compound offormula (IIa) with a base, for obtaining the chloro compound of formula:

R₁—(SO₂)—NM—(SO₂)—Cl  (IIb)

in which M represents a monovalent cation.14. The process as in embodiment 13, in which said base is chosen fromalkali metal carbonates, alkaline-earth metal carbonates, alkali metalhydroxides, alkaline-earth metal hydroxides, tertiary amines in a polarorganic solvent, and mixtures thereof.15. The process as in one of embodiments 1 to 14, comprising, after thesecond step:

(c) a third step of neutralization of the compound of formula (III),preferably by adding a base chosen from alkali metal carbonates,alkaline-earth metal carbonates, alkali metal hydroxides, alkaline-earthmetal hydroxides and mixtures thereof.

16. The process as in embodiment 15, in which the fluoro compound offormula (III) obtained in the second step is a compound of formula:

R₂—(SO₂)—NH—(SO₂)—F  (IIIa)

and in which the third step of neutralization allows the compound offormula (IIIa) to be converted into a compound of formula:

R₂—(SO₂)—NM—(SO₂)—F  (IIIb)

in which M represents a monovalent cation.17. The process as in one of embodiments 1 to 16, comprising, after thesecond step or, where appropriate, the third step, a final step ofcation exchange, preferably by placing in contact with an alkali metalor alkaline-earth metal or quaternary ammonium fluoride, chloride,carbonate, hydroxide, sulfate, chlorate, perchlorate, nitrite ornitrate.18. The process as in one of embodiments 1 to 17, for obtainingLiN(SO₂F)₂, LiN(SO₂CF₃)(SO₂F), LiN(SO₂C₂F₅)(SO₂F),LiN(SO₂CF₂OCF₃)(SO₂F), LiN(SO₂C₃HF₆)(SO₂F), LiN(SO₂C₄F₉)(SO₂F),LiN(SO₂C₅F₁₁)(SO₂F), LiN(SO₂C₆F₁₃)(SO₂F), LiN(SO₂C₇F₁₅)(SO₂F),LiN(SO₂C₈F₁₇)(SO₂F) or LiN(SO₂C₉F₁₉)(SO₂F), and preferably LiN(SO₂F)₂.19. A process for manufacturing an electrolyte, comprising thepreparation of an imide salt of formula (IIIb) R₂—(SO₂)—NM—(SO₂)—F, inwhich M represents a monovalent cation and R₂ represents anelectron-withdrawing group having a positive Hammett parameter σ_(p),via the process of one of embodiments 1 to 18, and dissolution thereofin a solvent, said imide salt preferably being a lithium, sodium orpotassium salt.20. A process for manufacturing a battery or a battery cell, comprisingthe manufacture of an electrolyte as in embodiment 19 and the insertionof this electrolyte between an anode and a cathode.21. A composition comprising at least 99.9% by mass of an imide salt offormula:

R₂—(SO₂)—NM—(SO₂)—F  (IIIb)

in which M represents a monovalent cation and R₂ represents anelectron-withdrawing group having a positive Hammett parameter σ_(p),the composition comprising a mass content of total fluorides of from 1to 500 ppm, and/or a mass content of total chlorides of from 1 to 200ppm.22. The composition as in embodiment 21, in which the mass content oftotal fluorides is from 1 to 250 ppm and/or the mass content of totalchlorides is from 1 to 100 ppm.23. The composition as in embodiment 21 or 22, comprising a mass contentof nitrates of less than or equal to 250 ppm, preferably less than orequal to 150 ppm; and/or comprising a mass content of sulfates of lessthan or equal to 250 ppm, preferably less than or equal to 150 ppm.24. The composition as in one of embodiments 21 to 23, in which:

-   -   M represents Li or Na or K and/or    -   R₂ represents F, CF₃, CHF₂, CH₂F, C₂HF₄, C₂H₂F₃, C₂H₃F₂, C₂F₅,        C₃F₇, C₃H₂F₅, C₃H₄F₃, C₃HF₆, C₄F₉, C₄H₂F₇, C₄H₄F₅, C₅F₁₁,        C₃F₆OCF₃, C₂F₄OCF₃, C₂H₂F₂OCF₃, CF₂OCF₃, C₆F₁₃, C₇F₁₅, C₈F₁₇ or        C₉F₁₉, F being preferred.        25. The composition as in one of embodiments 21 to 24, in which        the imide salt is LiN(SO₂F)₂, LiN(SO₂CF₃)(SO₂F),        LiN(SO₂C₂F₅)(SO₂F), LiN(SO₂CF₂OCF₃)(SO₂F), LiN(SO₂C₃HF₆)(SO₂F),        LiN(SO₂C₄F₉)(SO₂F), LiN(SO₂C₅F₁₁)(SO₂F), LiN(SO₂C₆F₁₃)(SO₂F),        LiN(SO₂C₇F₁₅)(SO₂F), LiN(SO₂C₈F₁₇)(SO₂F) or LiN(SO₂C₉F₁₉)(SO₂F),        and preferably LiN(SO₂F)₂.

1. A composition comprising at least 99.9% by mass of an imide salt offormula:R₂—(SO₂)—NM—(SO₂)—F  (IIIb) in which M represents a monovalent cationand R₂ represents an electron-withdrawing group having a positiveHammett parameter σ_(p), the composition comprising a mass content oftotal fluorides of from 1 to 500 ppm, and/or a mass content of totalchlorides of from 1 to 200 ppm.
 2. The composition as in claim 1, inwhich the mass content of total fluorides is from 1 to 500 ppm, and themass content of total chlorides is from 1 to 200 ppm.
 3. The compositionas in claim 1, in which the mass content of total fluorides is from 1 to250 ppm and/or the mass content of total chlorides is from 1 to 100 ppm.4. The composition as in claim 1, in which the mass content of totalfluorides is from 1 to 250 ppm and the mass content of total chloridesis from 1 to 100 ppm.
 5. The composition as in claim 1, comprising amass content of nitrates of less than or equal to 250 ppm; and/orcomprising a mass content of sulfates of less than or equal to 250 ppm.6. The composition as in claim 1, comprising a mass content of nitratesof less than or equal to 250 ppm; and comprising a mass content ofsulfates of less than or equal to 250 ppm.
 7. The composition as inclaim 1, comprising a mass content of nitrates of less than or equal to150 ppm; and/or comprising a mass content of sulfates of less than orequal to 150 ppm.
 8. The composition as in claim 1, comprising a masscontent of nitrates of less than or equal to 150 ppm; and comprising amass content of sulfates of less than or equal to 150 ppm.
 9. Thecomposition as in claim 1, in which: M represents Li or Na or K; and/orR₂ represents F, CF₃, CHF₂, CH₂F, C₂HF₄, C₂H₂F₃, C₂H₃F₂, C₂F₅, C₃F₇,C₃H₂F₅, C₃H₄F₃, C₃HF₆, C₄F₉, C₄H₂F₇, C₄H₄F₅, C₅F₁₁, C₃F₆OCF₃, C₂F₄OCF₃,C₂H₂F₂OCF₃, CF₂OCF₃, C₆F₁₃, C₇F₁₅, C₈F₁₇ or C₉F₁₉.
 10. The compositionas in claim 1, in which: M represents Li or Na or K; and R₂ representsF.
 11. The composition as in claim 1, in which the imide salt isLiN(SO₂F)₂, LiN(SO₂CF₃)(SO₂F), LiN(SO₂C₂F₅)(SO₂F),LiN(SO₂CF₂OCF₃)(SO₂F), LiN(SO₂C₃HF₆)(SO₂F), LiN(SO₂C₄F₉)(SO₂F),LiN(SO₂C₅F_(H))(SO₂F), LiN(SO₂C₆F₁₃)(SO₂F), LiN(SO₂C₇F₁₅)(SO₂F),LiN(SO₂C₈F₁₇)(SO₂F) or LiN(SO₂C₉F₁₉)(SO₂F)
 12. The composition as inclaim 1, in which the imide salt is LiN(SO₂F)₂.
 13. The composition asin claim 1, in which: the mass content of total fluorides is from 1 to250 ppm; and the mass content of total chlorides is from 1 to 100 ppm,the composition comprising: a mass content of nitrates of less than orequal to 250 ppm; a mass content of sulfates of less than or equal to250 ppm; a mass content of nitrates of less than or equal to 150 ppm;and a mass content of sulfates of less than or equal to 150 ppm, inwhich: M represents Li or Na or K; R₂ represents F; and the imide saltis LiN(SO₂F)₂.